1. Field of the Invention
This invention relates to human prosthetic limbs. More particularly, the present invention relates to an improved prosthetic ankle joint which allows resiliently resisted lateral rotation of the foot relative to the ankle, allowing more realistic freedom of motion for a user of the prosthetic device.
2. State of the Art
In recent years, prosthetic devices that more closely imitate real limbs in function and appearance have become more advanced and well known. These more advanced prostheses allow amputees and persons with defects of various kinds to lead more normal lives and participate in sports and recreational activities that they otherwise could not join. For example, many modern prosthetic foot/leg devices, such as those disclosed in U.S. Pat. No. 5,112,356 to Harris et al., U.S. Pat. No. 5,019,109 to Voisin, and U.S. Pat. No. 5,769,896 to Rosendahl et al. incorporate energy storing resilient feet which allow for more natural walking, and even running, jumping, and other athletic movements.
Many known devices also incorporate joints that allow plantar-dorsiflexion and lateral flexion of the foot relative to the leg. However, one common failure of many known prosthetic joints is that they do not allow for lateral rotation of the foot relative to the ankle. Of the known devices that do allow lateral rotation, many unnaturally constrain the rotation, such as in U.S. Pat. No. 3,956,775 to Moore, or allow rotation only in discrete increments, such as U.S. Pat. No. 4,865,611 to Al-Turaiki, or allow it in an unnatural manner, such as in U.S. Pat. Nos. 5,019,109 to Voisin and U.S. Pat. No. 5,030,239 to Copes. Such lateral rotation is desirable for athletic activities such as golf, basketball, and other sports where lateral rotation of the foot relative to the ankle is desirable. Moreover, resilient resistance to such rotation is desirable to approximate the function of the human ankle.